1. Field of the Invention
The present invention relates to a method and an apparatus for winding metal wires on a coiling structure (which is hereinafter referred to as "a spool"), and more particularly to a metal winding method and apparatus whereby, if the end portion of the metal wire wound on the spool springs back, the last group of coils near the wire end are prevented from becoming entangled with each other so as to facilitate drawing-out of the wire.
2. Description of the Prior Art
In the following description, the term "coil radius" signifies the expansion in a radial direction of the coil or the radius of the coil when the restraining force is released from the wire, and the word "coil pitch" means the distance between adjacent coils of the wire in the direction of the pitch when the coils are released from the restraining force.
Every type of metal wire wound on the spool is strained to have a certain radius. In the case of welding wire on the market, the wire is strained to have a certain coil radius and wound on the spool with its end fixed to the spool flange. This is accomplished to control the degree of the spring back action of the wire and to stabilize the feeding of the wire into a curved conduit tube. When this wire is to be unwound and used, the wire end is taken off the spool flange or is released from restraint by cutting the wire at the flange and then the wire end is conducted into a draw-out device. During this process, however, the smooth drawing-out of the wire is often blocked due to the spring-back action of the wire itself.
Wire materials such as welding wires are strained during the winding process to obtain a certain coil radius, but at the same time the coil pitch is adjusted to almost zero to ensure smooth feeding of the wire, for example, into the conduit tube. As long as the wire end is secured to the spool flange, the wire does not become loose. But if the wire end slips from a grip when it is being released from the flange, about 10 coils near the wire end spring back due to their own elastic force, with the result that they become entangled. This tendency is prominent in a reeled wire that has a smaller coil pitch. In the welding wire whose coil pitch is almost zero, several coils at the end of the wire gather and become entwined in one knot. This makes it difficult to draw out the wire end and if the wire end is drawn out with the coils entangled, the coils are squeezed so that the resistance against the drawing out of wire increases, thus causing the wire feeding to become unstable or in the worst case blocking the feeding. In the course of novelty search, the following U.S. Patents were located.
U.S. Pat. No. 4,019,359 to Smith, 3,587,274 to Rotter, 3,581,389 to Mori, 2,997,076 to McVoy, Jr., 2,739,763 to Silfverling et al, 2,265,246 to Ott and 1,258,092 to Clark.
U.S. Pat. No. 2,739,763 to Silfverlin et al discloses an apparatus for coiling cold rolled strips in which it is desired that the final turns of the strip be bent to such a curvature that the coil does not unwind to any appreciable extent. The strip is bent by a plurality of bending rolls mounted upon movable arms. The cylinder may be actuated to move the roller closer to rollers near the end of the strip so that the last few turns of the strip will have a smaller diameter and the strip will coil tightly about the coiler. Silfverlin et al patent therefore discloses the general idea of providing the last few turns of a coil strip with a diameter, or round habit, from the remainder of the strip for a specific purpose. Furthermore, Silfverlin et al suggests, on lines 43-46 of the column 2, that the tensioning of the strip will not lessen the amount of prebending or circular habit which is imparted upon a metal strip. This is contrary to the teaching of the present invention which discloses that the tensioning, or straining, of the strip will decrease the amount of prebending, thereby providing a larger diameter round habit.
U.S. Pat. No. 2,265,246 to Ott discloses a metal coil and a method for forming the same in which the last turn of the strip is given a lesser diameter by being progressively curled on a curling dye as it is wound on a core. The lesser diameter end portion of the coil is then allowed to curl adjacent the remainder of the coil. Ott discloses that the purpose of curling the end portion of the strip is to prevent a straight strip end which would become entangled with the remainder of the coil or with other coils prior to unwinding.
U.S. Pat. No. 4,019,359 to Smith discloses a method and apparatus for hot rolling metal strip. In Smith, the metal strip is prebent or given a round habit by a set of three bending rollers prior to being wound upon a coil. Furthermore, Smith discloses, at lines 60 and 61 of column 4, that the required degree of curl, or the required round habit, decreases as the amount of strip is fed onto the coil. Smith therefore generally suggests progressively increasing the diameter of the round habit of the strip as one approaches the end of the strip. However, the suggestion in Smith is for a gradual, progressive increase in the diameter of the round habit of the strip along the entire length of the strip while, in the present invention, only the last turn or the last few turns are given the larger diameter round habit. Furthermore, the round habit in Smith is not provided by means which strain the last few turns but rather is provided by traditional bending rollers.
The remainder of the cited references generally show prebending or tensioning means for metal wires or strips which are to be coiled, however, they are not believed to be as pertinent as the above references.